Semiconductor laser device and method of manufacturing the same

ABSTRACT

A semiconductor laser device includes a substrate and a semiconductor layer formed on a surface of the substrate and having a waveguide extending in a first direction parallel to the surface, wherein the waveguide is formed on a region approaching a first side from a center of the semiconductor laser device in a second direction parallel to the surface and intersecting with the first direction, a first region separated from the waveguide on a side opposite to the first side of the waveguide and extending parallel to the first direction and a first recess portion separated from the waveguide on an extension of a facet of the waveguide, intersecting with the first region and extending in the second direction are formed on an upper surface of the semiconductor laser device, and a thickness of the semiconductor layer on the first region is smaller than a thickness of the semiconductor layer on a region other than the first region.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of U.S. application Ser.No. 12/357,282 filed on Jan. 21, 2009.

The priority application number JP2008-10202, Semiconductor Laser Deviceand Method of Manufacturing the Same, Jan. 21, 2008, Ryoji Hiroyama etal, JP2009-6780, Semiconductor Laser Device and Method of Manufacturingthe Same, Jan. 15, 2009, Ryoji Hiroyama et al, upon which this patentapplication is based is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor laser device and amethod of manufacturing the same, and more particularly, it relates to asemiconductor laser device comprising a semiconductor layer providedwith a waveguide and a method of manufacturing the same.

2. Description of the Background Art

A nitride-based semiconductor laser device comprising a semiconductorlayer provided with a striped waveguide is known in general, asdisclosed in Japanese Patent Laying-Open No. 2003-17791, for example.

Referring to FIG. 29, a semiconductor layer 102 having a ridge portion102 a constituting a striped waveguide is formed on a GaN-basedsubstrate 101 in the conventional nitride-based semiconductor laserdevice 1000 disclosed in the aforementioned Japanese Patent Laying-OpenNo. 2003-17791. This ridge portion 102 a is provided at the center ofthe nitride-based semiconductor laser device in a cross direction(direction P). A p-side electrode 103 is provided on the semiconductorlayer 102. An n-side electrode 104 in ohmic contact with the GaN-basedsubstrate 101 is provided on a back surface of the GaN-based substrate101. Two mirror facets 105 and 106 consisting of cleavage planes areformed to be orthogonal to the ridge portion 102 a. These two mirrorfacets 105 and 106 constitute cavity facets.

Grooving portions 107 for cleavage introduction are formed on theGaN-based substrate 101, the semiconductor layer 102 and the p-sideelectrode 103. These grooving portions 107 are formed on the two mirrorfacets 105 and 106 consisting of the cleavage planes along a directionorthogonal to the ridge portion 102 a at the same distance in thedirection P leftwardly and rightwardly from the ridge portion 102 a, tohold the ridge portion 102 a provided at the center therebetween. Inother words, the grooving portions 107 are horizontally symmetricallyformed with respect to the ridge portion 102 a.

In this nitride-based semiconductor laser device, a metal wire 108 forsupplying power to the p-side electrode 103 is wire-bonded to the p-sideelectrode 103.

In general, the metal wire 108 is usually wire-bonded to the center ofthe p-side electrode 103. Particularly when the length in the crossdirection (direction P) is reduced due to downsizing of thenitride-based semiconductor laser device, the bonding position must bematched with the center, in order to increase allowance (margin) withrespect to displacement in wire bonding.

In the structure of the nitride-based semiconductor laser devicedisclosed in the aforementioned Japanese Patent Laying-Open No.2003-17791, however, the ridge portion 102 a is formed at the center ofthe nitride-based semiconductor laser device, and hence the metal wire108 is bonded to a portion immediately above the ridge portion 102 aprovided at the center when the metal wire 108 is bonded to the p-sideelectrode 103, if the length of the nitride-based semiconductor laserdevice in the cross direction (direction P) is reduced. Therefore, theridge portion 102 a (waveguide) is disadvantageously damaged in bondingof the metal wire 108 to deteriorate laser characteristics.

In the nitride-based semiconductor laser device, tensile stress isusually caused in an extensional direction of the waveguide and adirection orthogonal to this direction due to difference in latticeconstants between a GaN layer and an AlGaN layer in forming thesemiconductor layer. In the structure of the nitride-based semiconductorlaser device disclosed in the aforementioned Japanese Patent Laying-OpenNo. 2003-17791, therefore, microcracks voluntarily caused between thegrooving portions 107 in the form of broken lines formed on thesemiconductor layer 102 may be formed in the cross direction (directionP in FIG. 29) of the semiconductor laser device while causing steps inthe extensional direction of the waveguide (direction Q in FIG. 29) inthe vicinity of the ridge portion 102 a, when the wafer is cleaved inthe form of a bar. In this case, the semiconductor layer 102 is cleavedstarting from the microcracks having steps in the extensional direction(direction Q) of the waveguide, and hence the smooth cleavage planes(mirror facets 105 and 106) can not be obtained, and cleavage can not beexcellently performed. Therefore, the ridge portion 102 a (waveguide) isdisadvantageously damaged.

SUMMARY OF THE INVENTION

A semiconductor laser device according to a first aspect of the presentinvention comprises a substrate and a semiconductor layer formed on asurface of the substrate and having a waveguide extending in a firstdirection parallel to the surface, wherein the waveguide is formed on aregion approaching a first side from a center of the semiconductor laserdevice in a second direction parallel to the surface and intersectingwith the first direction, a first region separated from the waveguide ona side opposite to the first side of the waveguide and extendingparallel to the first direction and a first recess portion separatedfrom the waveguide on an extension of a facet of the waveguide,intersecting with the first region and extending in the second directionare formed on an upper surface of the semiconductor laser device, and athickness of the semiconductor layer on the first region is smaller thana thickness of the semiconductor layer on a region other than the firstregion.

In other words, the semiconductor laser device according to the firstaspect of the present invention comprises the substrate and thesemiconductor layer formed on the surface of the substrate and formedwith the waveguide extending in a prescribed direction, wherein thewaveguide is formed on the region approaching the first side from thecenter of the semiconductor layer, and the first concave region is soformed from the side of the semiconductor layer on the region of theside opposite to the first side of the waveguide at a prescribeddistance as to extend parallel to a prescribed extensional direction ofthe waveguide, and the first recess portion is so formed on theextension of the facet of the waveguide at a prescribed distance fromthe waveguide from the side of the semiconductor layer as to intersectwith the first concave region and to extend in a direction intersectingwith the prescribed extensional direction of the waveguide.

In the semiconductor laser device according to the first aspect, ashereinabove described, the waveguide extending in the prescribeddirection (first direction parallel to the surface of the substrate) isformed on the region approaching the first side from the center of thesemiconductor layer in the second direction parallel to the surface ofthe substrate and intersecting with the first direction. Thus, bondingof a metal wire onto the waveguide can be suppressed in a case ofbonding the metal wire to the center of an upper surface of thesemiconductor layer for supplying power to the upper surface of thesemiconductor layer, whereby damage of the waveguide can be suppressedin bonding. Consequently, deterioration of the laser characteristics canbe suppressed.

In this semiconductor laser device, the first region is so formed on theupper surface of the semiconductor laser device as to extend parallel tothe extensional first direction of the waveguide, and the thickness ofthe semiconductor layer on the first region is smaller than thethickness of the semiconductor layer on the region other than the firstregion. Thus, the semiconductor layer is divided in the second direction(cross direction of the semiconductor laser device) intersecting withthe extensional direction of the first region with respect to the firstregion employed as a center, and hence tensile stress caused in thesecond direction (cross direction of the semiconductor laser device) canbe rendered smaller than tensile stress caused in the extensionaldirection of the waveguide due to difference in the lattice constantsbetween the substrate and the semiconductor layer in forming thesemiconductor layer. Consequently, microcracks voluntarily causedbetween the first regions are inhibited from formation while causingsteps in the extensional direction of the waveguide. Thus, the cleavageis excellently performed along a plurality of the first recess portionsand the smooth cleavage planes (cavity facets) are obtained, and hencedamage of the waveguide can be suppressed.

In this semiconductor laser device, the first recess portion is soformed on the extension of the facet of the waveguide at the prescribeddistance from the waveguide from the side of the semiconductor layer asto intersect with the first region and to extend in the second directionintersecting with the extensional first direction of the waveguide. Inother words, the first recess portion is formed on the region on theextension of the facet of the waveguide at the distance from thewaveguide. Thus, the first recess portion can be formed on the positionseparated from the waveguide, and hence damage of the waveguide can besuppressed when the first recess portion is formed from the side of thesemiconductor layer. Thus, deterioration of the laser characteristics ofthe devices can be suppressed also by this.

A method of manufacturing a semiconductor laser device according to asecond aspect of the present invention comprises steps of forming asemiconductor layer including a plurality of waveguides extending in afirst direction parallel to the surface and first regions separated fromthe waveguides and extending parallel to the plurality of waveguides ona surface of a substrate, forming a plurality of first recess portionsintersecting with the first regions and extending in a second directionparallel to the surface and intersecting with the first direction onregions separated from the waveguides from a side of an upper surface ofthe semiconductor layer, performing cleavage along the plurality offirst recess portions, and forming chips by separating the semiconductorlayer along the first direction, wherein a thickness of thesemiconductor layer on the first region is smaller than a thickness ofthe semiconductor layer on a region other than the first region, andeach of the chips has the waveguide on a region approaching a first sidefrom a center of the chip in the second direction.

In other words, the method of manufacturing a semiconductor laser deviceaccording to the second aspect of the present invention comprises stepsof forming a semiconductor layer including a plurality of the waveguidesextending in a prescribed direction and the first concave regionsextending parallel to the plurality of waveguides on the surface of thesubstrate, forming a plurality of the first recess portions for cleavageintroduction between the plurality of waveguides from the side of thesemiconductor layer so as to intersect with the first concave regionsand to extend in a direction intersecting with the prescribedextensional direction of the waveguides, performing cleavage along theplurality of first recess portions and performing separation along theprescribed extensional direction of the waveguides so that eachsemiconductor laser device has the waveguide on the region approachingthe first side from the center of the semiconductor layer.

As hereinabove described, the method of manufacturing the semiconductorlaser device according to the second aspect comprises a step ofperforming separation so that each semiconductor laser device has thewaveguide on the region approaching the first side in the crossdirection from the center of the semiconductor layer. In other words,each of the chips formed by performing the separation step has thewaveguide on the region approaching the first side from the center ofthe chip in the second direction. Thus, bonding of a metal wire onto thewaveguide can be suppressed in a case of bonding the metal wire to thecenter of the side of an upper surface of the semiconductor layer forsupplying power to the upper surface of the semiconductor layer, wherebydamage of the waveguide can be suppressed in bonding. Consequently,deterioration of the laser characteristics can be suppressed.

The method of manufacturing the semiconductor device comprises a step offorming the semiconductor layer including the first regions extendingparallel to a plurality of the waveguides, and the thickness of thesemiconductor layer on the first region is rendered smaller than thethickness of the semiconductor layer on the region other than the firstregion. Thus, the semiconductor layer is divided by the first regions inthe second direction (cross direction of the semiconductor laser device)intersecting with the extensional direction of the first regions withrespect to the first regions employed as centers, and hence tensilestress caused in the second direction (cross direction of thesemiconductor laser device) can be rendered smaller than tensile stresscaused in the extensional direction of the waveguides due to differencein the lattice constants between the substrate and the semiconductorlayer in forming the semiconductor layer. Consequently, microcracksvoluntarily caused between the first recess portions are inhibited fromformation while causing steps in the extensional direction of thewaveguide at the time of the cleavage, whereby the cleavage isexcellently performed and the smooth cleavage planes (side surfacesincluding the facets of the waveguide forming the cavity facets) areobtained. Thus, damage of the waveguide can be suppressed.

In the manufacturing process of the semiconductor laser device, thefirst regions can inhibit nonuniformity of the crystal growth layer(local change of the thickness of the semiconductor layer) frominfluencing the vicinity of the regions formed with the waveguides whenthe first regions are formed on the positions separated by theprescribed distances from the waveguides by stacking the semiconductorlayer on the substrate, and hence deterioration of the lasercharacteristics of the devices can be further suppressed.

The method of manufacturing a semiconductor laser device comprises astep of forming the plurality of first recess portions between theplurality of waveguides from the side of the semiconductor layer so asto intersect with the first regions and to extend in the seconddirection intersecting with the extensional first direction of thewaveguides. In other words, the method of manufacturing a semiconductorlaser device comprises a step of forming the plurality of first recessportions intersecting with the first regions and extending in the seconddirection parallel to the surface and intersecting with the firstdirection from the side of the upper surface of the semiconductor layer.Thus, the first recess portions can be formed on the positions separatedfrom the waveguides and hence damage of the waveguides can be suppressedwhen the first recess portions are formed from the side of the uppersurface of the semiconductor layer. Thus, deterioration of the lasercharacteristics of the device can be suppressed also by this.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view for illustrating the concept of the presentinvention;

FIG. 2 is a plan view for illustrating the concept of the presentinvention;

FIG. 3 is another plan view for illustrating the concept of the presentinvention;

FIG. 4 is a perspective view showing the structure of a GaN-basedsemiconductor laser chip according to a first embodiment of the presentinvention;

FIG. 5 is a sectional view showing the detailed structure of asemiconductor layer of the GaN-based semiconductor laser chip shown inFIG. 4;

FIG. 6 is a sectional view for illustrating the manufacturing process(wafer process) in the wafer state of the GaN-based semiconductor laserchip according to the first embodiment shown in FIG. 4;

FIG. 7 is a plan view for illustrating the manufacturing process (waferprocess) in the wafer state of the GaN-based semiconductor laser chipaccording to the first embodiment shown in FIG. 4;

FIGS. 8 and 9 are perspective views for illustrating the manufacturingprocess (wafer process) in the wafer state of the GaN-basedsemiconductor laser chip according to the first embodiment shown in FIG.4;

FIG. 10 is a sectional view for illustrating the manufacturing process(separation process) subsequent to the wafer process for the GaN-basedsemiconductor laser chip according to the first embodiment shown in FIG.4;

FIG. 11 is a plan view for illustrating the manufacturing process(separation process) subsequent to the wafer process for the GaN-basedsemiconductor laser chip according to the first embodiment shown in FIG.4;

FIG. 12 is a sectional view for illustrating the manufacturing process(separation process) subsequent to the wafer process for the GaN-basedsemiconductor laser chip according to the first embodiment shown in FIG.4;

FIG. 13 is a perspective view showing the structure of a GaN-basedsemiconductor laser chip according to a first modification of the firstembodiment of the present invention;

FIG. 14 is a perspective view showing the structure of a GaN-basedsemiconductor laser chip according to a second modification of the firstembodiment of the present invention;

FIG. 15 is a plan view for illustrating the manufacturing process (waferprocess) of the GaN-based semiconductor laser chip according to thesecond modification of the first embodiment shown in FIG. 14;

FIG. 16 is a perspective view showing the structure of a GaN-basedsemiconductor laser chip according to a third modification of the firstembodiment of the present invention;

FIG. 17 is a plan view for illustrating the manufacturing process (waferprocess) of the GaN-based semiconductor laser chip according to thethird modification of the first embodiment shown in FIG. 16;

FIG. 18 is a perspective view showing the structure of the GaN-basedsemiconductor laser chip according to the second embodiment of thepresent invention;

FIG. 19 is a plan view for illustrating the manufacturing process (waferprocess) of the GaN-based semiconductor laser chip according to thesecond embodiment shown in FIG. 18;

FIG. 20 is a plan view for illustrating the manufacturing process (waferprocess) of a GaN-based semiconductor laser chip according to amodification of the second embodiment of the present invention;

FIG. 21 is a perspective view showing the structure of a GaN-basedsemiconductor laser chip according to a third embodiment of the presentinvention;

FIGS. 22 and 23 are a sectional view for illustrating the manufacturingprocess (wafer process) of the GaN-based semiconductor laser chipaccording to the third embodiment shown in FIG. 21;

FIG. 24 is a perspective view showing the structure of a GaN-basedsemiconductor laser chip according to a fourth embodiment of the presentinvention;

FIG. 25 is a plan view showing the structure of the GaN-basedsemiconductor laser chip according to the fourth embodiment shown inFIG. 24;

FIG. 26 is an enlarged sectional view around a cleavage introductionrecess portion formed through the manufacturing process for theGaN-based semiconductor laser chip according to the fourth embodimentshown in FIG. 24;

FIG. 27 is a perspective view showing the structure of a GaN-basedsemiconductor laser chip according to a fifth embodiment of the presentinvention;

FIG. 28 is a sectional view for illustrating the manufacturing process(wafer process) of the GaN-based semiconductor laser chip according tothe fifth embodiment shown in FIG. 27; and

FIG. 29 is a perspective view showing the structure of a conventionalnitride-based semiconductor laser device comprising a semiconductorlayer provided with a striped waveguide disclosed in Japanese PatentLaying-Open No. 2003-17791.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The concept of the present invention will be now described withreference to FIGS. 1 to 3, before describing specific embodiments of thepresent invention.

In a semiconductor laser device 100 according to an embodiment of thepresent invention, a semiconductor layer 2 having a current injectionregion 2 a constituting a waveguide extending in a prescribed direction(direction C: laser emission direction of the semiconductor laser device100) is formed on a substrate 1 in a region approaching a first side(side along arrow A) in the cross direction (along arrow A and alongarrow B) of the semiconductor laser device 100 from the center of thesubstrate 1, as shown in FIG. 1. The direction C which is the laseremission direction of the semiconductor laser device 100 and thedirection along arrow A (direction along arrow B) which is the crossdirection of the semiconductor laser device 100 are examples of the“first direction” or the “second direction” in the present inventionrespectively. The current injection region 2 a is an example of the“waveguide” in the present invention. A current blocking layer 3 isformed on the semiconductor layer 2 except an upper surface of thecurrent injection region 2 a. A first electrode 4 in ohmic contact withthe current injection region 2 a of the semiconductor layer 2 isprovided on the current blocking layer 3. A second electrode 5 in ohmiccontact with the substrate 1 is provided on a back surface of thesubstrate 1. Two cleavage planes 6 and 7 are formed to be orthogonal tothe current injection region 2 a (waveguide).

Cleavage introduction steps 8 a and 8 b for performing cleavage areformed on the semiconductor layer 2, the current blocking layer 3 andthe first electrode 4. These cleavage introduction steps 8 a and 8 b areformed only on a region opposite (on a side along arrow B) to the firstside (side along arrow A) of the current injection region 2 a on thecleavage planes 6 and 7 which are extensions of facets of the currentinjection region at a prescribed interval from the current injectionregion 2 a (waveguide), to extend in a direction (along arrow A (alongarrow B)) orthogonal to the current injection region 2 a (waveguide). Inthe semiconductor layer 2, a groove portion 9 is so formed from the sideof the upper surface of the semiconductor layer 2 toward the substrate 1on the region of the upper surface of the semiconductor laser device 100on a side opposite (on the side along arrow B) to the first side (sidealong arrow A) of the current injection region 2 a as to extend in adirection (direction C) parallel to the current injection region 2 a.The groove portion 9 is so formed as to intersect with the cleavageintroduction steps 8 a and 8 b. The first electrode 4 and the secondelectrode 5 are examples of the “first electrode layer” and the “secondelectrode layer” in the present invention respectively. The cleavageintroduction steps 8 a and 8 b are examples of the “first recessportion” in the present invention and the groove portion 9 is an exampleof the “first region” in the present invention. The groove portions 9are preferably formed so as not to protrude from ends of the cleavageintroduction steps 8 a and 8 b in a longitudinal direction (along arrowA) to the current injection regions 2 a. Thus, the groove portions 9 andthe cleavage introduction steps 8 are arranged so that microcracks 10 bcan be easily formed between the cleavage introduction steps 8 adjacentto each other along arrow A (along arrow B) in FIG. 3 described later.

In this semiconductor laser device 100, as hereinabove described, thecurrent injection region 2 a constituting the waveguide extending in thelaser emission direction (direction C) parallel to the surface of thesubstrate 1 is formed on the region approaching the first side (sidealong arrow A) in the cross direction (along arrow A (along arrow B)),parallel to the surface of the substrate 1 and intersecting with thedirection C, of the semiconductor laser device 100 from the center ofthe semiconductor layer 2. Thus, bonding of a metal wire onto thewaveguide can be suppressed in a case of bonding the metal wire to thecenter of the upper surface of the semiconductor layer 2 for supplyingpower to the upper surface of the semiconductor layer 2, whereby damageof the waveguide can be suppressed in bonding. Consequently,deterioration of the laser characteristics can be suppressed.

The substrate 1 consists of a semiconductor having a hexagonal structurecontaining a nitride, and may consist of GaN, AlN, InN, BN, TlN oralloyed semiconductors of these. The substrate 1 may have n-typeconductivity, or may have p-type conductivity. In relation to the planeorientation of the substrate 1, a substrate of a {0001} plane, a {11-22}plane, a {11-20} plane or a {1-100} plane can be employed. In this case,the cleavage planes 6 and 7 are preferably formed by the {1-100} planeor the {0001} plane, in view of planarity of the cleavage planes 6 and 7and easiness in cleavage.

The semiconductor layer 2 includes at least a layer of a conductivitytype different from that of the substrate 1. This semiconductor layer 2may include an active layer. In this case, the semiconductor layer 2 mayhave the layer of the conductivity type different from that of thesubstrate 1 on the surface of the active layer opposite to the substrate1. Further, the active layer may be held between two layers ofconductivity types different from each other, having larger band gapsthan the active layer. In this case, one of the two layers ofconductivity types different from each other may be the substrate 1.

At least one layer in the semiconductor layer 2 has a lattice constantsmaller than the substrate. In this case, tensile stress is applied onthe semiconductor layer 2 in directions (along arrow A, along arrow Band in the direction C) parallel to the surface of the semiconductorlayer 2, as shown in FIG. 2. The cleavage introduction steps 8 areformed in the form of broken lines in the direction (along arrow A(along arrow B)) orthogonal to the extensional direction of thewaveguide in a manufacturing process in a state where the tensile stressin the extensional direction (direction C) of the waveguide exists,thereby causing microcracks 10 (shown by broken lines in FIG. 2) betweenthe cleavage introduction steps 8 adjacent to each other. Then, cleavageis performed along the cleavage introduction steps 8 and hence thecleavage is excellent as compared with a case where no cleavageintroduction step 8 is formed. In this state, however, the tensilestress having substantially the same strength as the tensile stressapplied in the extensional direction C of the waveguide is caused alsoin the direction (along arrow A (along arrow B)) orthogonal to theextensional direction of the waveguide, and hence microcracks 10 a(shown by broken lines) extend while locally causing steps in theextensional direction C of the waveguide as shown in FIG. 2. In thiscase, the smooth cleavage planes may not be formed on the semiconductorlayer 2.

In this semiconductor laser device 100, the groove portions 9 (shown bythick lines in FIG. 2) are formed to extend parallel to the extensionaldirection (direction C) of the current injection region 2 a on thesurface of the semiconductor layer 2, so that the thickness of thesemiconductor layer 2 on the groove portion 9 is smaller than thethickness of the semiconductor layer 2 on the region other than thegroove portion 9. In other words, the groove portion 9 divides thesemiconductor layer 2 (see FIG. 1) in the direction along arrow A (alongarrow B) which is orthogonal to the extensional direction of thewaveguide, as shown in FIG. 3. Thus, the tensile stress along arrow A(along arrow B) is reduced as compared with the tensile stress in thedirection C and hence formation of the microcracks 10 a having steps asshown in FIG. 2 is eliminated. As shown in FIG. 3, linear microcracks 10b (shown by broken lines in FIG. 2) are formed along arrow A (alongarrow B) starting from the cleavage introduction steps 8 adjacent toeach other. Consequently, the semiconductor layer 2 (see FIG. 1) iscleaved starting from the linear microcracks 10 b, and hence cleavage ofthe semiconductor layer 2 is more excellently performed and the smoothcleavage planes 6 and 7 are obtained. Thus, damage of the waveguide canbe suppressed.

In this semiconductor laser device 100, the cleavage introduction steps8 a and 8 b are so formed on the extensions of the cleavage planes 6 and7 formed as facets of the waveguide at a prescribed interval from thecurrent injection region 2 a constituting the waveguide from the side ofthe semiconductor layer 2 as to intersect with the groove portion 9 andto extend in a direction intersecting with a prescribed extensionaldirection of the waveguide. In other words, the cleavage introductionsteps 8 a and 8 b are formed on the regions on the extensions of thecleavage planes 6 and 7 at a distance from the waveguide. Thus, thecleavage introduction steps 8 a and 8 b can be formed on positionsseparated from the waveguide, and hence damage of the waveguide can besuppressed when the cleavage introduction steps 8 a and 8 b are formedfrom the side of the upper surface of the semiconductor layer 2. Thus,deterioration of the laser characteristics can be suppressed also bythis.

The current injection region 2 a may be formed by a ridge portion havinga convex sectional shape as shown in FIG. 1, or an opening (not shown)extending in the direction C may be provided on the current blockinglayer 3 without providing the convex ridge portion, for connecting thecurrent injection region 2 a defined by the opening and the firstelectrode 4 with each other through the opening.

The current injection region 2 a is preferably formed along the <1-100>direction (direction C) orthogonal to the {1-100} plane which is theplane orientation capable of obtaining an excellent cleavage plane.

The semiconductor layer 2 consists of a semiconductor having a hexagonalstructure containing a nitride, and may consist of GaN, AlN, InN, BN,TlN or alloyed semiconductors of these. The band gaps of the respectivelayers (the layer of the conductivity type different from that of thesubstrate 1, the active layer, the two layers of conductivity typesdifferent from each other etc.) constituting the semiconductor layer 2can be set to desired values by varying the ratios of the materials andthe alloyed semiconductors constituting the layers.

Carbon, oxygen, silicon, sulfur, germanium, selenium or tellurium can beemployed as a dopant introduced into an n-type substrate 1 and n-typelayers of the semiconductor layer 2, while beryllium, magnesium or zinccan be employed as a dopant introduced into a p-type substrate 1 andp-type layers of the semiconductor layer 2.

The current blocking layer 3 is employed for blocking current injectioninto the regions other than the current injection region 2 a, and can beformed by an insulator or a high-resistance material. More specifically,an oxide or a nitride of aluminum, silicon, titanium, zinc, gallium,zirconium, indium or hafnium can be employed.

The first electrode 4 and the second electrode 5 are ohmic electrodesfor supplying power to the current injection region 2 a and thesubstrate 1 respectively, and both are made of materials havingconductivity. The first electrode 4 and the second electrode 5 may beconstituted of aluminum, silicon, titanium, chromium, nickel, germanium,rhodium, palladium, silver, indium, tin, platinum, gold or an alloythereof, or multilayer structures obtained by stacking layers of these.The first electrode 4 and the second electrode 5 may be formed atprescribed intervals from the cleavage planes 6 and 7. Further, thefirst electrode 4 and the second electrode 5 may be formed at prescribedintervals from the side surfaces (side surfaces parallel to thewaveguide) of the device.

The cleavage introduction steps 8 a and 8 b are recess portions fornormally performing cleavage, and may be formed by scratching with ahard tool such as a diamond point having a sharp forward end, or may beformed by applying a beam such as a laser beam or an ion beam havinghigh energy to only desired regions thereby evaporating the material ofthese portions.

Embodiments embodying the aforementioned concept of the presentinvention will be hereinafter described with reference to the drawings.

(First Embodiment)

The structure of a GaN-based semiconductor laser chip (device) 200according to a first embodiment will be now described with reference toFIGS. 4 and 5. The GaN-based semiconductor laser chip 200 according tothe first embodiment is a 400 nm-band semiconductor laser chip (violetlaser diode).

In the GaN-based semiconductor laser chip 200 according to the firstembodiment, a semiconductor layer 12 including an active layer 24 (seeFIG. 5) described later and having a p-n junction is formed on asubstrate 11 made of n-type GaN, as shown in FIG. 4. This semiconductorlayer 12 includes a ridge portion 12 a constituting a waveguideextending in a direction C in a striped (slender) manner. The directionC is a laser emission direction of the GaN-based semiconductor laserchip 200 and is an example of the “first direction” in the presentinvention. The ridge portion 12 a is an example of the “waveguide” inthe present invention.

The GaN-based semiconductor laser chip 200 has a first device sidesurface 201 parallel to the extensional direction C of the ridge portion12 a and a second device side surface 202 opposed to the first deviceside surface 201 and parallel to the direction C, and the second deviceside surface 202 and the first device side surface 201 are formed on aside along arrow A and a side along arrow B in a direction (along arrowA (along arrow B)) orthogonal to the direction C respectively. Thedirection along arrow A (direction along arrow B) is the cross directionof the GaN-based semiconductor laser chip 200 and is an example of the“second direction” in the present invention.

According to the first embodiment, a groove portion 30 extending in adirection parallel to the extensional direction (direction C) of theridge portion 12 a is formed on the upper surface of the GaN-basedsemiconductor laser chip 200 from a side of the semiconductor layer 12as shown in FIG. 4. The groove portion 30 is so formed as to overlap agroove portion 11 a formed on the surface of the substrate 11 in amanufacturing process described later. The groove portion 30 is soformed as to have a width W0 (=about 10 μm) along arrow A from a facet(first device side surface 201) of the GaN-based semiconductor laserchip 200 on the side along arrow B and to have a depth D0 (=about 5 μm)from an upper surface of the GaN-based semiconductor laser chip 200 tothe substrate 11. The groove portion 30 is an example of the “firstregion” in the present invention. FIG. 4 slightly exaggeratingly shows athickness of the semiconductor layer 12 constituting the groove portion30. The groove portion 11 a formed on the surface of the substrate 11 isan example of the “third recess portion” in the present invention.

As shown in FIG. 4, the GaN-based semiconductor laser chip 200 is soformed that a length (width) along arrow A (along arrow B) is about 200μm and a length (depth) in the direction C is about 400 μm. A cleavagedirection (direction substantially orthogonal to the ridge portion 12 a)(along arrow A (along arrow B)) is a <11-20> direction. A plane(cleavage plane 17 or 18 described later) emitting a laser beam is an Mplane ({1-100} plane).

According to the first embodiment, the ridge portion 12 a is formed on aregion approaching a first side (side along arrow A) by a distance W1(=about 30 μm) from a center 600 (shown by a one-dot chain line in FIG.4) of the GaN-based semiconductor laser chip 200 along arrow A (alongarrow B), and is formed inward by a prescribed distance W2 (=about 70μm) from an end of the first side (side along arrow A) of the GaN-basedsemiconductor laser chip 200. A p-side electrode 13 obtained by stackinga Pt film and a Pd film successively from the side of the ridge portion12 a is formed on the upper surface of this ridge portion 12 a. Acurrent blocking layer 14 made of an SiO₂ film having a thickness ofabout 300 nm is formed on the semiconductor layer 12, to cover thep-side electrode 13. An opening 14 a is provided on a region of thiscurrent blocking layer 14 immediately above the p-side electrode 13other than the vicinity of both ends (cleavage planes 17 and 18described later) in the direction C. A p-side pad electrode 15 obtainedby stacking a Ti film and an Au film successively from the sides of thep-side electrode 13 and the current blocking layer 14 is formed onregions of the p-side electrode 13 and the current blocking layer 14enclosed with lines inward by about 30 μm from the facets (four surfacesof the first device side surface 201, the second device side surface 202and the cleavage planes 17 and 18) of the GaN-based semiconductor laserchip 200. The p-side pad electrode 15 is an example of the “firstelectrode layer” in the present invention. This p-side pad electrode 15is so formed that the length (width) along arrow A (along arrow B) isabout 140 μm and the length (depth) in the direction C is about 340 μm.An n-side electrode 16 obtained by stacking a Ti film, a Pt film and anAu film successively from the side of the substrate 11 is formed on theback surface of the GaN-based semiconductor laser chip 200. The n-sideelectrode 16 is an example of the “second electrode layer” in thepresent invention.

In the GaN-based semiconductor laser chip 200, two cleavage planes 17and 18 are formed to be orthogonal to the ridge portion 12 aconstituting the waveguide. These two cleavage planes 17 and 18constitute cavity facets of the GaN-based semiconductor laser chip 200.

According to the first embodiment, cleavage introduction steps 19 a and19 b for performing cleavage having a depth D1 (about 20 μm) are formedon boundaries between the cleavages 17 and 18 in the substrate 11, thesemiconductor layer 12 and the current blocking layer 14 from the uppersurface of the GaN-based semiconductor laser chip 200, as shown in FIG.4. The cleavage introduction steps 19 a and 19 b are examples of the“first recess portion” in the present invention. These cleavageintroduction steps 19 a and 19 b are formed only on a region of a side(side along arrow B) opposite to the first side (side along arrow A) ofthe ridge portion 12 a at a prescribed interval W3 (at least about 70μm) from the ridge portion 12 a (waveguide) along the direction (alongarrow A (along arrow B)) orthogonal to the ridge portion 12 a(waveguide).

More specifically, each of the cleavage introduction steps 19 a and 19 bis so formed at a prescribed distance W3 (=about 90 μm) along arrow Bfrom the ridge portion 12 a (waveguide) as to reach the facet alongarrow B of the GaN-based semiconductor laser chip 200. Each of thecleavage introduction steps 19 a and 19 b has a width W4 (=about 40 μm)along arrow B.

According to the first embodiment, the cleavage introduction steps 19 aand 19 b are formed on a region not provided with the p-side padelectrode 15.

According to the first embodiment, separation introduction steps 20 aand 20 b for performing separation are formed on ends of the substrate11 and the n-side electrode 16 along arrow A and along arrow B (in thevicinity of boundaries between the substrate 11 and the n-side electrode16 and the second device side surface 202 and the first device sidesurface 201) along the extensional direction (direction C) of the ridgeportion 12 a (waveguide) from the back surface of the GaN-basedsemiconductor laser chip 200, as shown in FIG. 4. The separationintroduction steps 20 a and 20 b are examples of the “second recessportion” in the present invention.

According to the first embodiment, a region where the groove portion 30of the cleavage plane 17 (18) and the cleavage introduction step 19 a(19 b) intersect with each other has a depth D2 of about 25 μm. In otherwords, a dip deeper than the groove portion 30 and the cleavageintroduction step 19 a (19 b) is partially formed in the vicinity of theboundary between the cleavage plane 17 (18) and the first device sidesurface 201.

As to the detailed structures of the substrate 11 and the semiconductorlayer 12, the substrate 11 made of n-type GaN is doped with oxygen, andconsists of a hexagonal structure. The semiconductor layer 12 has a mainsurface consisting of a C plane (plane orientation (0001)) of a Gasurface. In the semiconductor layer 12, a buffer layer 21 arranged onthe substrate 11 and consisting of a Ge-doped n-type GaN layer isformed, as shown in FIG. 5. An n-type cladding layer 22 of n-typeAl_(0.05)Ga_(0.95)N is formed on this buffer layer 21.

An n-side optical guide layer 23 of undoped GaN is formed on the n-typecladding layer 22. An active layer 24 having a multiple quantum well(MQW) structure is formed on this n-side optical guide layer 23. Thisactive layer 24 has a structure obtained by alternately stacking twobarrier layers (not shown) of undoped GaN and three well layers (notshown) of undoped In_(0.1)Ga_(0.9)N.

A p-side optical guide layer 25 of undoped GaN is formed on the activelayer 24. A cap layer 26 of undoped Al_(0.3)Ga_(0.7)N is formed on thisp-side optical guide layer 25. This cap layer 26 has a function ofsuppressing deterioration of the crystal quality of the active layer 24by suppressing desorption of In atoms of the active layer 24.

A p-type cladding layer 27, doped with Mg, of p-type Al_(0.05)Ga_(0.95)Nis formed on the cap layer 26. This p-type cladding layer 27 has aprojecting portion, formed by etching a prescribed region from the uppersurface of the p-type cladding layer 27, having a width of about 1.5 μmand extending in the direction C (see FIG. 4). A p-side contact layer 28of undoped In_(0.05)Ga_(0.9)N is formed on the projecting portion of thep-type cladding layer 27. The projecting portion of the p-type claddinglayer 27 and the p-side contact layer 28 form the ridge portion 12 abecoming a current injection region and having a function as thewaveguide. FIG. 5 slightly exaggeratingly shows thicknesses of therespective layers of the semiconductor layer 12 constituting the grooveportion 30.

A manufacturing process (wafer process) in a wafer state of theGaN-based semiconductor laser chip 200 according to the first embodimentwill be now described with reference to FIGS. 5 to 9.

As shown in FIG. 6, the groove portions 11 a having widths W5 (abouttwice the width W0) of about 20 μm and depths D3 of about 5 μm areformed on the main surface of the substrate 11 made of n-type GaN. Thegroove portions 11 a are so formed in a striped manner at intervals W6(=about 400 μm) along arrow A (along arrow B) as to extend in thedirection C orthogonal to the direction along arrow A (along arrow B),as shown in FIG. 7. In a step of forming the groove portions 11 a, anSiO₂ film (not shown) is formed on the main surface of the substrate 11by EB deposition, and striped openings are formed on the SiO₂ film byphotolithography and etching. Thereafter the striped groove portions 11a (see FIG. 7) are formed on the substrate 11 employing the SiO₂ film asa mask by RIE. The groove portions 11 a are examples of the “thirdrecess portion” in the present invention.

After the SiO₂ film (not shown) is removed, the buffer layer 21consisting of the Ge-doped n-type GaN layer, the n-type cladding layer22 of n-type Al_(0.05)Ga_(0.95)N and the n-side optical guide layer 23of undoped GaN are successively grown on the substrate 11 by MOVPE(Metal Organic Vapor Phase Epitaxy) at a substrate temperature of about1150° C., as shown in FIGS. 5 and 6.

Thereafter the active layer 24 is formed by alternately growing thethree well layers (not shown) of undoped In_(0.1)Ga_(0.9)N and the twobarrier layers (not shown) of undoped GaN on the n-side optical guidelayer 23 by MOVPE at a substrate temperature of about 850° C. Then, thep-side optical guide layer 25 of undoped GaN and the cap layer 26 ofundoped Al_(0.3)Ga_(0.7)N are successively formed on the active layer24.

Thereafter the p-type cladding layer 27, doped with Mg, of p-typeAl_(0.05)Ga_(0.95)N is grown on the cap layer 26 by MOVPE at a substratetemperature of about 1150° C.

Then, the p-side contact layer 28 of undoped In_(0.05)Ga_(0.95)N isformed on the p-type cladding layer 27 by MOVPE at a substratetemperature of about 850° C.

According to the first embodiment, the groove portion 30 is formed inthe semiconductor layer 12 on each groove portion 11 a formed on thesubstrate 11 in a state where a crystal growth layer (semiconductorlayer 12) has a thickness extremely thinner than a crystal growth layerformed on the main surface except the groove portion 11 a, as shown inFIG. 6. The groove portion 30 is an example of the “first region” in thepresent invention. In this case, the semiconductor layer 12 is dividedin the direction along arrow A (along arrow B) by the groove portion 30,whereby tensile stress in the direction along arrow A (along arrow B)perpendicular to the extensional direction (direction C in FIG. 7) ofthe groove portion 11 a applied to the semiconductor layer 12 isrelaxed. The crystal growth layer (semiconductor layer 12) is so formedas to thickly rise in the vicinity of the groove portion 30, and thefilm thickness and the film composition of this portion on thesemiconductor layer 12 are different from those of a region of thesemiconductor layer 12 separated from the groove portion 30 along arrowA (along arrow B). The reason why crystal growth is performed in thismanner is conceivable as follows:

The inner side surfaces of each groove portion 11 a are a (11-20) planedifferent from the (0001) plane which is the main surface of thesubstrate 11 made of n-type GaN, and hence the growth rate of thecrystal growth layer (semiconductor layer 12) is conceivably low due tothe difference in the plane orientation. On the other hand, the mainsurface of the substrate 11 in the vicinity of the groove portion 11 a,which is not formed with the groove portion 11 a, or the bottom portionof the groove portion 11 a is the (0001) plane identical with the mainsurface of the substrate 11, and hence the crystal growth of thesemiconductor layer 12 should be performed similarly to a regionsufficiently separated from the groove portion 11 a. However, respectiveconstituent atoms which should be originally supplied to the bottomportion of the groove portion 11 a are not supplied to the bottomportion of the groove portion 11 a due to some kind of influence by theinner side surfaces ((11-20) plane) of the groove portion 11 a, whilethe constituent atoms are supplied on the main surface of the substrate11 in the vicinity of the groove portion 11 a. Consequently, thesemiconductor layer 12 thickly grows on the main surface of thesubstrate 11 in the vicinity of the groove portions 11 a, and hence thecrystal growth layer (semiconductor layer 12) is conceivably formed soas to thickly rise in the vicinity of the inner side surfaces of thegroove portion 30 as shown in FIG. 6.

Each groove portion 11 a formed on the substrate 11 before the crystalgrowth is preferably so formed that the depth D3 is at least thethickness of the semiconductor layer 12, in order for the groove portion30 to divide the semiconductor layer 12 in the direction along arrow A(along arrow B) as described above. In this case, each groove portion 11a is preferably so formed that the width W5 is about 10 μm to about 30μm. FIG. 7 shows a state where groove portions 30 (hatched regions) areformed on the groove portions 11 a of the substrate 11 (see FIG. 6).

Thereafter the ridge portions 12 a and the p-side electrodes 13 areformed by employing vacuum evaporation and etching. More specifically,the Pt film and the Pd film are formed on the p-side contact layer 28 byvacuum evaporation successively from the p-side contact layer 28. Then,etching is employed for etching the Pt film and the Pd film through amask of photoresist (not shown) extending in the direction C (see FIG.4), and etching the p-side contact layer 28 and a prescribed region fromthe upper surface of the p-type cladding layer 27. Thus, the two ridgeportions 12 a having the widths of about 1.5 μm constituted by thep-side contact layer 28 and the projecting portions of the p-typecladding layer 27 and the p-side electrodes 13 arranged on therespective ridge portions 12 a are formed between a plurality of thegroove portions as shown in FIG. 5.

According to the first embodiment, at this time, the ridge portions 12 a(shown by broken lines in FIG. 7) are so formed as to extend in thedirection (<1-100> direction) (direction C) substantially orthogonal tothe <11-20> direction (along arrow A (along arrow B)) which is thecleavage direction as shown in FIG. 7. The ridge portions 12 a are soformed on positions separated from the centers of the groove portions 11a (groove portions 30) formed on the substrate 11 at the intervals W6(=about 400 μm) along arrow A and along arrow B by about 130 μm(=W3+W4). Therefore, the ridge portions 12 a are so formed alternatelyat two different intervals, i.e., intervals W7 (=about 140 μm) andintervals W8 (=about 260 μm). Thus, the semiconductor layer 12consisting of the buffer layer 21, the n-type cladding layer 22, then-side optical guide layer 23, the active layer 24, the p-side opticalguide layer 25, the cap layer 26, the p-type cladding layer 27 and thep-side contact layer 28 is formed as shown in FIG. 5.

Thereafter the current blocking layer 14 made of the SiO₂ film havingthe thickness of about 300 nm is formed on the semiconductor layer 12 byplasma CVD to cover the A-side electrodes 13, as shown in FIG. 8.

Then, etching is employed for etching the current blocking layer 14through a mask of photoresist (not shown), for forming openings 14 a(see FIG. 8) on portions of the current blocking layer 14 formed onregions other than regions for forming the cleavage planes 17 and 18 inthe regions immediately above the p-side electrodes 13. Thus, the uppersurfaces of the p-side electrodes 13 are exposed.

Thereafter p-side pad electrodes 15 are formed by stacking Ti films andAu films on upper portions of the A-side electrodes 13 exposed on theopening 14 a and prescribed regions of the current blocking layer 14successively from the side of the p-side electrodes 13 and the currentblocking layer 14 by vacuum evaporation and a lift-off method, as shownin FIG. 9. More specifically, photoresist film (not shown) is formed ona region of the current blocking layer 14 other than regions enclosedwith lines inward by about 30 μm from positions for forming the facets(four surfaces of the first device side surface 201, the second deviceside surface 202 and the cleavage planes 17 and 18) of the GaN-basedsemiconductor laser chip 200. Then, the Ti films and the Au films areformed on the A-side electrodes 13 and the current blocking layer 14successively from the p-side electrodes 13 and the current blockinglayer 14 by vacuum evaporation. Thereafter the photoresist film (notshown) is removed by the lift-off method, whereby the p-side padelectrodes 15 are formed on the regions of the p-side electrodes 13 andthe current blocking layer 14 enclosed with the lines inward by about 30μm from the positions (see FIG. 4) for forming the facets (four surfacesof the first device side surface 201, the second device side surface 202and the cleavage planes 17 and 18) of the GaN-based semiconductor laserchip 200. At this time, the p-side pad electrodes 15 are so formed thatthe ridge portions 12 a constituting waveguides are arranged on regionsapproaching sides (sides along arrow B) opposite to the first sides(sides along arrow A) by about 30 μm from the centers of the p-side padelectrodes 15 along arrow A (along arrow B). Each p-side pad electrode15 is so formed that the length (width) along arrow A (along arrow B) isabout 140 μm and the length (depth) in the direction C is about 340 μm.

Then, the back surface of the substrate 11 is polished until thethickness of the substrate 11 reaches about 100 μm, for example.Thereafter the n-side electrode 16 is formed on the back surface of thesubstrate 11 by stacking the Ti film, the Pt film and the Au filmsuccessively from the substrate 11 by vacuum evaporation, as shown inFIG. 9. A wafer having GaN-based semiconductor laser chips 200 arrangedin the form of a matrix is completed in the aforementioned manner.

A manufacturing process (separation process) subsequent to the waferprocess for the GaN-based semiconductor laser chip 200 according to thefirst embodiment will be now described with reference to FIGS. 4, 6, 7and 9 to 12.

According to the first embodiment, cleavage introduction recess portions19 extending in the direction (along arrow A and along arrow B)orthogonal to the ridge portions 12 a are formed at intervals of about400 μm along the extensional direction (direction C) of the stripedridge portions 12 a from the side of the semiconductor layer 12 with adiamond point or a laser beam, as shown in FIG. 7. At this time, eachcleavage introduction recess portion 19 is so formed as to be orthogonalto the groove portion 30 and extend along arrow A and along arrow B fromthe central position of the groove portion 30 by 40 μm (corresponding toW4 in FIG. 4). The cleavage introduction steps 19 a and 19 b areexamples of the “first recess portion” in the present invention. At thistime, the cleavage introduction recess portions 19 are formed on regionsnot provided with the p-side pad electrodes 15, whereby development ofmetal swarfs or the like can be suppressed when forming the same withthe diamond point or the laser beam. Thus, the p-side layers (the p-sideoptical guide layer 25, the cap layer 26, the p-type cladding layer 27,the p-side contact layer 28, the p-side electrodes 13 and the p-side padelectrodes 15) and the n-side layers (the n-side electrode 16, thesubstrate 11, the buffer layer 21, the n-type cladding layer 22 and then-side optical guide layer 23) can be inhibited from electricallyshort-circuiting by metal swarfs or the like.

According to the first embodiment, the cleavage introduction recessportions 19 are not formed on regions within about 70 μm along arrow Aor along arrow B from the ridge portions 12 a but the centers of thecleavage introduction recess portions 19 along arrow A (along arrow B)are formed at a distance W3+W4 (=90+40=about 130 μm) from the adjacentridge portions 12 a (waveguides). Thus, reduction of the distancebetween the cleavage introduction recess portions 19 and the ridgeportions 12 a can be suppressed, whereby damage of the ridge portions 12a can be suppressed when forming the cleavage introduction recessportions 19. Further, the cleavage introduction recess portions 19 areso formed as to have depths D1 (=about 20 μm) on regions where thecleavage introduction recess portions 19 and the groove portions 30 donot intersect with each other and to have depths D2 (=about 25 μm) onregions where the cleavage introduction recess portions 19 and thegroove portions 30 intersect with each other. In other words, thegrooves portions 30 are formed on the substrate 11, the semiconductorlayer 12 and the current blocking layer 14 from the upper surface of theGaN-based semiconductor laser chip 200, and the substrate 11 is exposedon the bottom portions of the groove portions 30. In the state beforethe wafer is cleaved, the cleavage introduction recess portions 19 arein the form of grooves.

In this state, the wafer is cleaved on the position of each cleavageintroduction recess portion 19 along arrow A (along arrow B) (see FIG.9) by applying a load while fulcruming the side of the lower surface(back surface) of the substrate 11 so that the side of the upper surface(formed with the semiconductor layer 12 with respect to the substrate11) of the wafer opens, as shown in FIG. 10. Thus, the wafer is formedinto a bar having the GaN-based semiconductor laser chips 200 alignedwith each other along arrow A (along arrow B), as shown in FIG. 11. Atthis time, the wafer is cleaved while fulcruming the side of the lowersurface of the substrate 11 so that the side of the upper surface opens,whereby application of the load to the ridge portions 12 a of thesemiconductor layer 12 can be suppressed. Thus, mechanical damage of theridge portions 12 a of the semiconductor layer 12 can be suppressed,whereby deterioration of the laser characteristics can be suppressed.

Then, separation introduction recess portions 20 are formed at intervalsof about 200 μm in the extensional direction (direction C) (see FIG. 11)of the striped ridge portions 12 a from the back surface of thesubstrate 11 of the wafer cleaved in the form of a bar with the diamondpoint or the laser beam, as shown in FIGS. 11 and 12. At this time, theseparation introduction recess portions 20 are formed on every secondregion opposed to the groove portion 30 (see FIG. 7) in the thicknessdirection of the substrate 11. Thus, each separation introduction recessportion 20 is formed also on a region opposed to the center of theadjacent ridge portions 12 a having a smaller interval W7 among theridge portions 12 a alternately having the different two intervals.Consequently, the separation introduction recess portions 20 arearranged on the regions opposed to the positions separated by about 70μm and about 130 μm from both sides of each ridge portion 12 arespectively. Further, the separation introduction recess portions 20are formed on the substrate 11 and the n-side electrode 16 from the sideof the back surface of the GaN-based semiconductor laser chip 200. Theseparation introduction recess portions 20 can be formed at prescribeddistances from the ridge portions 12 a not only in the thicknessdirection (vertical direction) but also in the cross direction withrespect to the substrate 11, whereby damage of the ridge portions 12 acan be suppressed when forming the separation introduction recessportions 20. Further, separation of the wafer can be more easilyperformed on portions of the substrate 11 having small thicknessesreduced due to the groove portions 30 and the separation introductionrecess portions 20 which are opposed to each other, than on portions ofthe separation introduction recess portions 20 which are not opposed tothe groove portions 30. In the state before the wafer cleaved in theform of a bar is separated, the separation introduction recess portions20 are in the form of grooves. The separation introduction recessportions 20 are examples of the “second recess portion” in the presentinvention.

In this state, the bar-shaped wafer is separated on the position of eachseparation introduction recess portion 20 along arrow C (see FIG. 11) byapplying a load while fulcruming the side of the semiconductor layer 12(the side of upper side) so that the side of the lower surface (backsurface) of the GaN-based semiconductor laser chip 200 opens, as shownin FIG. 12. Thus, the bar-shaped wafer is separated into the GaN-basedsemiconductor laser chip 200 (200 a) having the length (width) of about200 μm along arrow A (along arrow B) and the length (depth) of about 400μm in the direction C as shown in FIG. 4, thereby manufacturing a largenumber of the GaN-based semiconductor laser chips 200.

According to the first embodiment, the two GaN-based semiconductor laserchips 200 and 200 a having a symmetrical shape in the direction alongarrow A (along arrow B) with respect to the separation introductionrecess portion 20 employed as a symmetrical axis are obtained.

According to the first embodiment, as hereinabove described, the ridgeportion 12 a constituting the waveguide extending in the direction C inthe striped (slender) manner is formed on the region approaching thefirst side (side along arrow A) by the distance W1 (=about 30 μm) fromthe center of the semiconductor layer 12 along arrow A (along arrow B)orthogonal to the direction C. Thus, bonding of a metal wire onto theridge portion 12 a constituting the waveguide can be suppressed in acase of bonding the metal wire to the center of the upper surface of thesemiconductor layer 12 for supplying power to the upper surface of thesemiconductor layer 12, whereby damage of the ridge portion 12 aconstituting the waveguide can be suppressed in bonding. Consequently,deterioration of the laser characteristics can be suppressed.

According to the first embodiment, the groove portion 30 is so formed onthe surface of the semiconductor layer 12 as to extend parallel to theextensional direction C of the ridge portions 12 a and the thickness ofthe semiconductor layer 12 on the groove portion 30 is smaller than thethickness of the semiconductor layer 12 on the region other than thegroove portion 30, and hence the semiconductor layer 12 is divided bythe groove portion 30 in the direction (along arrows A and B) orthogonalto the extensional direction (direction C) of the groove portion 30 withrespect to the center of the groove portion 30. Thus, tensile stresscaused along arrow A (along arrow B) (in the extensional direction ofthe cavity facets) perpendicular to the direction C can be renderedsmaller than tensile stress caused in the extensional direction C of theridge portions 12 a due to difference in the lattice constants betweenthe substrate 11 (GaN) and the semiconductor layer 12 (AlGaN) in formingthe semiconductor layer. Consequently, microcracks voluntarily causedbetween the cleavage introduction recess portions 19 adjacent to eachother can be inhibited from formation while causing steps in thedirection C, whereby the cleavage is excellently performed along aplurality of the cleavage introduction recess portions 19 and the smoothcleavage planes 17 and 18 (cavity facets) are obtained. Thus, damage ofthe ridge portion 12 a constituting the waveguide can be suppressed.

In the manufacturing process of the GaN-based semiconductor laser chip200, when the groove portions 30 are formed by stacking thesemiconductor layer 12 on the substrate 11 while covering the recessedgroove portions 11 a previously formed on the main surface of thesubstrate 11, the groove portions are formed at prescribed intervalsfrom the vicinity of regions formed with the ridge portions 12 a(waveguides) so that nonuniformity of the crystal growth layer caused bythe groove portions 30 can be inhibited from influencing the ridgeportions 12 a, and hence deterioration of the laser characteristics ofthe devices can be further suppressed.

According to the first embodiment, the cleavage introduction steps 19 aand 19 b (cleavage introduction recess portions 19) are formed only onthe regions of the sides (sides along arrow B) opposite to the firstsides of the ridge portions 12 a from the side of the semiconductorlayer 12 (upper side) and the cleavage introduction steps 19 a and 19 b(cleavage introduction recess portions 19) are not formed on the regionson the first sides (sides along arrow A) of the ridge portions 12 a,whereby the cleavage introduction steps 19 a and 19 b (cleavageintroduction recess portions 19) can be formed at the regions separatedfrom the ridge portions 12 a constituting the waveguides and hencedamage of the ridge portions 12 a constituting the waveguides can besuppressed when forming the cleavage introduction steps 19 a and 19 b(cleavage introduction recess portions 19) from the side of thesemiconductor layer 12 (upper side). This also can suppressdeterioration of the laser characteristics.

According to the first embodiment, the p-side pad electrode 15 is formedon the region enclosed with the lines inward by about 30 μm from thecleavage introduction steps 19 a and 19 b (cleavage introduction recessportions 19) so that the p-side pad electrode 15 and the cleavageintroduction steps 19 a and 19 b are formed at the prescribed intervalof about 30 μm, whereby a leakage current can be inhibited from increaseresulting from adhesion of a conductive material forming the p-side padelectrode 15 to the cleavage introduction steps 19 a and 19 b also whenthe conductive material constituting the A-side pad electrode 15scatters.

According to the first embodiment, the separation introduction steps 20a and 20 b extending in the direction C are formed on the back surfaceof the substrate 11, whereby the thicknesses of the portions of thesubstrate 11, which are formed with the separation introduction steps 20a and 20 b, are reduced and hence separation of the wafer can be easilyperformed on the portions formed with the separation introduction steps20 a and 20 b along the direction C at the time of separation in themanufacturing process.

According to the first embodiment, the separation introduction step 20 bis provided on the position of the back surface of the substrate 11opposed to the groove portion, whereby the thickness of the substrate 11can be further reduced due to the groove portion 30 and the separationintroduction step 20 b and hence separation of the wafer can be furthereasily performed along the direction C.

According to the first embodiment, the groove portion 11 a extendingparallel to the first direction (direction C) is formed on the region ofthe surface of the substrate 11 opposed to the groove portion 30,whereby the substrate 11 can be easily separated on the portion of thegroove portion 11 a along the direction C. The thickness of thesemiconductor layer 12 formed on the groove portion 11 a, that is, thethickness of the semiconductor layer 12 on the groove portion 30 can berendered smaller than the thickness of the semiconductor layer 12 formedon other region, and hence division of the semiconductor layer 12 in thedirection along arrow A (direction along arrow B) can be easilyperformed on the groove portion 30 on the groove portion 11 a.

According to the first embodiment, the depth D3 (=about 5 μm) of thegroove portion 11 a is rendered larger than the thickness of thesemiconductor layer 12, whereby the groove portion 30 for separating thesemiconductor layer 12 in the direction along arrow A (along arrow B)can be easily formed on the semiconductor layer 12 which iscrystal-grown on the surface of the substrate 11.

According to the first embodiment, the groove portion 30 is formed toreach a part of the substrate 11 from the surface of the semiconductorlayer 12, whereby separation can be easily performed on the portion ofthe substrate 11 having a small thickness reduced due to the grooveportion 30 at the time of separation.

According to the first embodiment, the groove portion 30 is so formedthat the width in the direction (along arrow A) orthogonal to theextensional direction (direction C) of the ridge portion 12 a isincreased upward so that ends of the semiconductor layer 12 (inner sidesurfaces of the groove portion 30) bent due to separation are unlikelyto come into contact with each other when performing separation so as toopen the lower surface of the bar-shaped wafer (back surface of thesubstrate 11), and hence damage of the semiconductor layer 12 at thetime of the separation can be suppressed.

According to the first embodiment, the cleavage introduction steps 19 aand 19 b are so formed that the width in the direction (along arrow A(along arrow B)) orthogonal to the extensional direction of the ridgeportion 12 a is increased upward so that energy for forming ends of thecleavage introduction steps 19 a and 19 b by laser application or thelike can be reduced below energy for forming the bottom portions of thecleavage introduction steps 19 a and 19 b by laser application or thelike, whereby a thermal influence on the ridge portion 12 a close to theends of the cleavage introduction steps 19 a and 19 b can be suppressed,and deterioration of the ridge portion 12 a can be suppressed.

According to the first embodiment, the groove portion 30 and thecleavage introduction step 19 a (19 b) are so formed that the depth D2(=about 25 μm) on the region where the groove portion 30 and thecleavage introduction step 19 a (19 b) intersect with each other islarger than the depth D0 (=about 5 μm) of the groove portion 30 and thedepth D1 (=about 20 μm) of the cleavage introduction step 19 a (19 b) onthe region where the groove portion 30 and the cleavage introductionstep 19 a (19 b) do not intersect with each other, whereby cleavage isperformed starting from the cleavage introduction recess portions 19more deeply formed up to the inside of the substrate 11 when cleavingthe bar-shaped wafer in the manufacturing process and hence the smoothcleavage planes 17 and 18 (cavity facets) can be further easilyobtained.

According to the first embodiment, the separation introduction steps 20a and 20 b are so formed as to have the length substantially identicalto the length between the cleavage planes 17 and 18 of the ridge portion12 a (waveguide), whereby separation of the wafer can be reliablyperformed in the extensional direction C of the separation introductionsteps 20 a and 20 a when forming the GaN-based semiconductor laser chip200 by separation.

According to the first embodiment, the separation introduction steps 20a and 20 b are formed on the n-side electrode 16 and the substrate 11 sothat the separation introduction step 20 a (20 b) reaches a part of thesubstrate 11 from the lower surface of the n-side electrode 16, wherebyseparation can be easily performed on the portion of the substrate 11having a small thickness reduced due to the separation introduction step20 a (20 b) when performing separation in the manufacturing process.

According to the first embodiment, the substrate 11 and thesemiconductor layer 12 are formed by a nitride-based semiconductor suchas GaN, whereby the GaN-based semiconductor laser chip 200 in whichdamage of the waveguide and deterioration of the laser characteristicsare suppressed can be formed.

The manufacturing process according to the first embodiment comprises astep of performing separation so that the GaN-based semiconductor laserchip 200 has the waveguide on the region approaching the first side(side along arrow A) in the cross direction from the center of thesemiconductor layer 12. In other words, the ridge portion 12 aconstituting the waveguide located between the first device side surface201 and the second device side surface 202 of the semiconductor layer 12formed by performing the separation step is arranged on the regionapproaching the side of the second device side surface 202 from thecenter of the semiconductor layer 12. Thus, bonding of the metal wireonto the ridge portion 12 a constituting the waveguide can be suppressedin a case of bonding the metal wire to the center of the side of theupper surface of the semiconductor layer 12 for supplying power to theupper surface of the semiconductor layer 12, whereby damage of the ridgeportion 12 a constituting the waveguide can be suppressed in bonding.Consequently, deterioration of the laser characteristics can besuppressed.

The manufacturing process according to the first embodiment comprises astep of forming the semiconductor layer 12 including the groove portions30 extending parallel to a plurality of the waveguides (ridge portions12 a) and the thickness of the semiconductor layer 12 on the grooveportion 30 is smaller than the thickness of the semiconductor layer 12on the region other than the groove portion 30. Thus, the semiconductorlayer 12 is divided by the groove portions 30 in the direction (crossdirection of the semiconductor laser device) orthogonal to theextensional direction (direction C) of the groove portions 30 withrespect to the groove portions 30 employed as centers. Thus, tensilestress caused in the direction (cross direction of the semiconductorlaser device) orthogonal to the extensional direction of the waveguidecan be rendered smaller than tensile stress caused in the extensionaldirection (direction C) of the waveguides due to difference in thelattice constants between the substrate 11 and the semiconductor layer12 in forming the semiconductor layer. Consequently, microcracksvoluntarily caused between the cleavage introduction recess portions 19can be inhibited from formation while causing steps in the extensionaldirection of the waveguide at the time of the cleavage, whereby thecleavage is excellently performed and the smooth cleavage planes 17 and18 (side surfaces including the facets of the waveguide forming thecavity facets) are obtained. Thus, damage of the ridge portion 12 aconstituting the waveguide can be suppressed.

In the manufacturing process according to the first embodiment, when thegroove portions 30 are formed on the positions separated by theprescribed distances from the waveguides by stacking the semiconductorlayer 12 on the substrate 11, the groove portions are formed atprescribed intervals from the vicinity of regions formed with the ridgeportions 12 a (waveguides) so that nonuniformity of the crystal growthlayer caused by the groove portions 30 can be inhibited from influencingthe ridge portions 12 a, and hence deterioration of the lasercharacteristics of the devices can be further suppressed.

The manufacturing process according to the first embodiment comprises astep of forming the plurality of cleavage introduction recess portions19 between the plurality of waveguides (ridge portions 12 a) from theside of the semiconductor layer 12 so as to intersect with the grooveportions 30 and to extend in the direction (along arrow A (along arrowB)) orthogonal to the prescribed extensional direction of the waveguides(the first direction (direction C) parallel to the surface of thesubstrate 11). In other words, the manufacturing process according tothe first embodiment comprises a step of forming a plurality of thecleavage introduction recess portions 19 intersecting with the grooveportions 30 and extending in the direction (along arrow A (along arrowB)) orthogonal to the first direction (direction C) on the regions ofthe surface of the semiconductor layer 12 between a plurality of thewaveguides at distances from the waveguides. Thus, the cleavageintroduction recess portions 19 can be formed on the positions separatedfrom the waveguides and hence damage of the ridge portions 12 aconstituting the waveguides can be suppressed when forming the cleavageintroduction recess portions 19 from the side of the semiconductor layer12. This also can suppress deterioration of the laser characteristics.

In the manufacturing process according to the first embodiment, the stepof the semiconductor layer 12 includes a step of forming a plurality ofthe ridge portions 12 a (waveguides) alternately having different twointervals W7 and W8 and the groove portions 30 located between theadjacent ridge portions 12 a (waveguides) having larger intervals W8(=about 260 μm) among the two intervals, whereby each ridge portion 12 a(waveguide) located between the first device side surface 201 and thesecond device side surface 202 of the semiconductor layer 12 formed bythe separation step can be easily arranged on the region approaching theside of the side surface 202 from the center of the semiconductor layer12.

In the manufacturing process according to the first embodiment, theseparation step is performed along the groove portions 30, whereby thewafer is separated along the groove portions 30 separated from thepositions formed with the ridge portions 12 a (waveguides) and hencedamage of the ridge portions 12 a can be easily suppressed at the timeof separation.

In the manufacturing process according to the first embodiment, a stepof forming the separation introduction recess portions 20 extendingparallel to the first direction (direction C) on the side of the backsurface of the substrate 11 opposite to the surface of the substrate isperformed in advance of the separation step, whereby separation can bereliably performed on the portions of the substrate 11 having smallthicknesses reduced due to the groove portions 30 and the separationintroduction recess portions 20 which are opposed to each other to holdthe substrate 11 therebetween along the direction C.

In the manufacturing process according to the first embodiment, theseparation introduction recess portions 20 are formed on the regionsopposed to the groove portions 30 and the separation step is performedalong the groove portions 30 and the separation introduction recessportions 20, whereby the thickness of the substrate 11 can be furtherreduced due to the groove portions 30 and the separation introductionrecess portions 20 and hence separation of the wafer can be furthereasily performed along the direction C.

In the manufacturing process according to the first embodiment, theseparation step includes a step of performing the separation so that thecleavage introduction steps 19 a (19 b) are provided on the regions onthe sides (sides along arrow B) opposite to the first sides (sides alongarrow A) formed with the ridge portions 12 a (waveguides), whereby theGaN-based semiconductor laser chips 200 are obtained in a state wherethe cleavage introduction steps 19 a (19 b) are kept away from theregions arranged with the ridge portions 12 a (waveguides) to the sidesalong arrow B. Consequently, bonding positions of the metal wires can bedetermined so as not to damage the ridge portions 12 a by observingplaner positions of the cleavage introduction steps 19 a (19 b).

Further, the cleavage introduction steps 19 a (19 b) can be formed onthe positions separated from the ridge portions 12 a (waveguides), andhence damage of the ridge portion 12 a (waveguides) can be suppressedwhen forming the cleavage introduction steps 19 a (19 b) from the sidesof the ridge portions 12 a. Thus, deterioration of the lasercharacteristics can be suppressed also by this. Only sizes of theregions of the portions having the cleavage introduction steps 19 a (19b) increase in the GaN-based semiconductor laser chips 200, and hencehandling of the device in the manufacturing process can be easilyperformed.

In the manufacturing process according to the first embodiment, the stepof forming the semiconductor layer 12 includes a step of forming therecessed groove portions 11 a extending parallel to the first direction(direction C) on the surface of the substrate 11 and a step ofcrystal-growing the semiconductor layer 12 on the surface of thesubstrate 11 formed with the groove portions 11 a, whereby the crystalgrowth rate of the semiconductor layer 12 deposited on the grooveportions 11 a and the crystal growth rate of the semiconductor layer 12deposited on the surface of the substrate 11 other than the grooveportions 11 a can be controlled and hence the groove portions 30 formedby the semiconductor layer 12 and dividing the semiconductor layer 12 inthe direction along arrow A (along arrow B) can be easily formed on thegroove portions 11 a.

In the manufacturing process according to the first embodiment, the stepof crystal-growing the semiconductor layer 12 includes a step ofcrystal-growing the semiconductor layer 12 having a thickness smallerthan the depths D3 (=about 5 μm) of the groove portions 11 a, wherebydifference between the crystal growth rate of the semiconductor layer 12deposited on the groove portions 11 a and the crystal growth rate of thesemiconductor layer 12 deposited on the surface of the substrate 11other than the groove portions 11 a can become more remarkable and hencethe groove portions 30 formed by the semiconductor layer 12 can bereliably formed on the groove portions 11 a.

(First Modification of First Embodiment)

Referring to FIG. 13, in a GaN-based semiconductor laser chip 205according to a first modification of the first embodiment, cleavageintroduction steps 19 a and 19 b having depths not reaching a substrate11 are formed on a semiconductor layer 12 dissimilarly to theaforementioned first embodiment. The cleavage introduction steps 19 aand 19 b are examples of the “first recess portion” in the presentinvention.

In the GaN-based semiconductor laser chip (device) 205 according to thefirst modification of the first embodiment, cleavage introduction steps19 c and 19 d for performing cleavage having depths D11 (about 15 μm)are formed on boundaries between the cleavages 17 and 18 in thesemiconductor layer 12 and a current blocking layer 14 from an uppersurface of the GaN-based semiconductor laser chip 205, as shown in FIG.13. In other words, in a separation process of the GaN-basedsemiconductor laser chip 205, the cleavage introduction steps 19 c and19 d are so formed as to have bottom portions which do not reach thesubstrate 11 on regions where the cleavage introduction steps 19 c and19 d do not intersect with a groove portion 30 and to have depths D21(=about 20 μm) on regions where the cleavage introduction steps 19 c and19 d intersect with the groove portion 30.

The remaining structure and manufacturing process of the GaN-basedsemiconductor laser chip 205 according to the first modification of thefirst embodiment are similar to those of the aforementioned firstembodiment, and the effects thereof are also similar to those of theaforementioned first embodiment.

(Second Modification of First Embodiment)

Referring to FIGS. 12, 14 and 15, in a GaN-based semiconductor laserdevice according to a second modification of the first embodiment, threeGaN-based semiconductor laser chips (devices) 210, 210 a and 210 b areobtained between a separation introduction recess portion 20 on aposition opposed to one groove portion 30 and a separation introductionrecess portion 20 adjacent thereto along arrow A (along arrow B) byseparation, dissimilarly to the manufacturing process of theaforementioned first embodiment.

The GaN-based semiconductor laser chip according to the secondmodification of the first embodiment is so formed that one GaN-basedsemiconductor laser chip 210 b is obtained in addition to the GaN-basedsemiconductor laser chip 210 (210 a) having a device structure similarto that of the aforementioned first embodiment, as shown in FIG. 14. Aridge portion 12 a of the GaN-based semiconductor laser chip 210 b isformed on a region approaching a first side (side along arrow B) from acenter of the device. The semiconductor layer structure of the GaN-basedsemiconductor laser chip 210 b is similar to that of the GaN-basedsemiconductor laser chip 210.

In other words, in a manufacturing process according to the secondmodification of the first embodiment, three ridge portions 12 aextending in a striped manner in a <1-100> direction (direction C) areformed between the groove portions 30 (portions shown by slant lines)adjacent to each other in a <11-20> direction (along arrow A (alongarrow B)) in a wafer process, as shown in FIG. 15. The three ridgeportions 12 a are formed at intervals W21, W22 and W23 in this orderalong arrow A and along arrow B from the center of each of the grooveportions 11 a (groove portions 30) which are formed on a substrate 11 atan interval W20. Therefore, the adjacent two ridge portions 12 a alongarrow A (along arrow B) to hold the groove portion 30 therebetween areso formed as to have a maximum interval (W24 (=W21+W21)) in the threeintervals between the adjacent ridge portions 12 a. The lengths of theintervals between the ridge portions 12 a adjacent to each other arereduced in order of W24>W23>W22.

In a separation process after cleavage in the form of a bar, separationintroduction recess portions 220 (two portions) extending in thedirection C are formed between adjacent p-side pad electrodes 15 on aregion of an interval W22 and between adjacent p-side pad electrodes 15on a region of an interval W23 respectively in addition to formation ofseparation introduction recess portions 20 on positions opposed to thegroove portions 30, and the chip-shaped GaN-based semiconductor laserchips 210 a, 210 b and 210 are thereafter obtained in this order througha method similar to the separation method shown in FIG. 12.

(Third Modification of First Embodiment)

Referring to FIGS. 12, 16 and 17, in a GaN-based semiconductor laserchip according to a third modification of the first embodiment, fourGaN-based semiconductor laser chips (devices) 210, 210 a, 210 b and 210c are obtained between a separation introduction recess portion 20 on aposition opposed to one groove portion 30 and a separation introductionrecess portion 20 adjacent thereto along arrow A (along arrow B) byseparation, dissimilarly to the aforementioned second modification ofthe first embodiment.

The GaN-based semiconductor laser chip according to the thirdmodification of the first embodiment is so formed that two GaN-basedsemiconductor laser chips 210 b and 210 c are obtained in addition tothe GaN-based semiconductor laser chip 210 (210 a) having a devicestructure similar to that of the aforementioned first embodiment, asshown in FIG. 16. The semiconductor layer structure of the GaN-basedsemiconductor laser chip 210 c is similar to that of the GaN-basedsemiconductor laser chip 210 b.

In other words, in a manufacturing process according to the thirdmodification of the first embodiment, four ridge portions 12 a extendingin a striped manner in a <1-100> direction are formed between the grooveportions 30 adjacent to each other in a <11-20> direction in a waferprocess, as shown in FIG. 17. The four ridge portions 12 a are formed atintervals W31, W32, W33 and W32 in this order along arrow A and alongarrow B from the center of each of the groove portions 11 a (grooveportions 30) which are formed on a substrate 11 at an interval W30.Therefore, the two ridge portions 12 a adjacent to each other alongarrow A (along arrow B) to hold the groove portion 30 therebetween areso formed as to have a maximum interval (W34 (=W31+W31)) in theintervals between the adjacent ridge portions 12 a. The lengths of theintervals between the ridge portions 12 a adjacent to each other arereduced in order of W34≧W33>W32.

In a separation process after cleavage in the form of a bar, separationintroduction recess portions 220 (three portions) extending in thedirection C are formed between adjacent p-side pad electrodes 15 on aregion of an interval W32 and between adjacent p-side pad electrodes 15on a region of an interval W33 respectively in addition to formation ofseparation introduction recess portions 20 on positions opposed to thegroove portions 30, and the chip-shaped GaN-based semiconductor laserchips 210 a, 210 c, 210 b and 210 are thereafter obtained in this orderthrough a method similar to the separation method shown in FIG. 12.

The effects of the aforementioned second and third modifications of thefirst embodiment are similar to those of the aforementioned firstembodiment.

(Second Embodiment)

Referring to FIG. 18, a GaN-based semiconductor laser chip 250 accordingto a second embodiment is formed with a substrate 41 made of n-type GaNincluding a region having a large number of linear crystal defectsdissimilarly to the aforementioned first embodiment. The substrate 41made of n-type GaN employed in the second embodiment is a substratelinearly concentrically forming crystal defects on a prescribed regionthereby reducing the number of crystal defects in the remaining wideregions.

In the GaN-based semiconductor laser chip (device) 250 according to thesecond embodiment, a semiconductor layer 42 including a ridge portion 42a constituting a waveguide extending in a direction C in a striped(slender) manner is formed on a substrate 41 made of n-type GaN as shownin FIG. 18, similarly to the aforementioned first embodiment. The ridgeportion 42 a is an example of the “waveguide” in the present invention.

According to the second embodiment, a region 60 having a large number ofcrystal defects is formed in the vicinity of ends of the substrate 41and the semiconductor layer 42 on a side along arrow B. As shown in FIG.18, a groove portion 70 extending in a direction parallel to anextensional direction (direction C) of a ridge portion 42 a is formed onthe substrate 41 from the side of the semiconductor layer 42 to includethe region 60. The groove portion 70 is so formed as to overlap on thegroove portion 41 a formed on the surface of the substrate 41 in themanufacturing process described later. The groove portion 70 is anexample of the “first region” in the present invention, and the grooveportion 41 a is an example of the “third recess portion” in the presentinvention. FIG. 18 slightly exaggeratingly shows a thickness of thesemiconductor layer 42 constituting the groove portion 70.

Two cleavage planes 47 and 48 constituting cavity facets of theGaN-based semiconductor laser chip 250 are formed to be orthogonal tothe ridge portion 42 a constituting the waveguide.

Cleavage introduction steps 49 a and 49 b having lengths of about 60 μmalong arrow A (along arrow B) are formed on the substrate 41, thesemiconductor layer 42 and a current blocking layer 44 to extend up toan end of the GaN-based semiconductor laser chip 250 on the side alongarrow B, similarly to the aforementioned first embodiment. The cleavageintroduction steps 49 a and 49 b are examples of the “first recessportion” in the present invention.

According to the second embodiment, separation introduction steps 50 aand 50 b for performing separation are formed on the substrate 41 and ann-side electrode 16 from the back surface of the GaN-based semiconductorlaser chip 250 along an extensional direction (direction C) of the ridgeportion 42 a, similarly to the aforementioned first embodiment. Theseparation introduction steps 50 a and 50 b are examples of the “secondrecess portion” in the present invention. The remaining structure of thesecond embodiment is similar to that of the aforementioned firstembodiment.

A manufacturing process (wafer process) in a wafer state of theGaN-based semiconductor laser chip 250 according to the secondembodiment will be now described with reference to FIGS. 18 and 19.

As shown in FIG. 18, a groove portion 41 a having a width (groove width)of about 40 μm and a depth of about 5 μm, extending in the direction Cis formed on a main surface of the substrate 41 made of n-type GaN byetching through a process similar to the aforementioned firstembodiment. At this time, the groove portion 41 a is so formed as toinclude the region 60, having a large number of crystal defects, of thesubstrate 41 according to the second embodiment.

Thereafter the layers up to a p-side contact layer (not shown) areformed on the substrate 41. In this case, a region of the semiconductorlayer 42 formed on the region 60, having a large number of crystaldefects, of the substrate 41 also defines the region 60 having a largenumber of crystal defects as shown in FIG. 19, according to the secondembodiment. FIG. 19 shows that the groove portion 70 (hatched region) ofthe semiconductor layer 42 is so formed as to include the region 60having a large number of crystal defects.

Then, the ridge portion 42 a and a p-side electrode 13 are formedthrough a process similar to the aforementioned first embodiment. Atthis time, a plurality of the ridge portions 42 a are so formed as toalternately have two different intervals, i.e., prescribed intervals W9(=about 140 μm) and W10 (=about 260 μm) as shown in FIG. 19.

According to the second embodiment, the ridge portions 42 a (waveguides)are so formed that regions 60, having large numbers of crystal defects,of the substrate 41 and the semiconductor layer 42 are arranged onintermediate positions between the ridge portions 42 a (waveguides)having the larger interval W10 (=about 260 μm) in the different twointervals, as shown in FIG. 19. The remaining manufacturing process(wafer process) in a wafer state and separation process after the waferprocess according to the second embodiment are similar to themanufacturing processes of the aforementioned first embodiment. Thus, alarge number of the GaN-based semiconductor laser chips 250 and 250 a(see FIG. 18) having device widths of about 200 μm and lengths of about400 μm in the direction C are manufactured.

In the manufacturing process according to the second embodiment, ashereinabove described, the plurality of ridge portions 42 a are soformed that the regions 60, having large numbers of crystal defects, ofthe substrate 41 and the semiconductor layer 42 are located on theintermediate positions between the adjacent ridge portions 42 a havingthe larger interval W10 (=about 260 mm) in the different two intervalsW9 and W10 so that the ridge portions 42 a can be formed on positionsseparated from the regions 60, having large numbers of crystal defects,of the substrate 41 and the semiconductor layer 42, whereby crystaldefects of the substrate 41 and the semiconductor layer 42 can beinhibited from propagating to the ridge portions 42 a constituting thewaveguides. Thus, reduction in reliability of the GaN-basedsemiconductor laser chip 250 can be suppressed.

According to the second embodiment, the groove portions 70 are so formedon the upper regions of the regions 60, having large numbers of crystaldefects, of the substrate 41 from the side of the semiconductor layer 42as to extend parallel to the extensional direction C of the ridgeportions 42 a, and the thickness of the semiconductor layer 42 on thegroove portion 70 is smaller than the thickness of the semiconductorlayer 42 on the region other than the groove portion 70, whereby thegroove portions 70 divide the semiconductor layer 42 in the direction(direction along arrow A (direction along arrow B)) perpendicular to theextensional direction (direction C) of the groove portions 70 withrespect to the groove portions 70 employed as centers. Thus, tensilestress caused along arrow A (along arrow B) perpendicular to thedirection C can be rendered smaller than tensile stress caused in theextensional direction C of the ridge portions 42 a due to difference inthe lattice constants between the substrate 41 (GaN) and thesemiconductor layer 42 (AlGaN) in forming the semiconductor layer.Consequently, microcracks voluntarily caused between the cleavageintroduction recess portions 49 adjacent to each other can be inhibitedfrom formation while causing steps in the direction C, whereby thecleavage is excellently performed along a plurality of the cleavageintroduction recess portions 49 and the smooth cleavage planes 47 and 48(cavity facets) are obtained. Thus, damage of the ridge portion 42 aconstituting the waveguide can be suppressed. The remaining effects ofthe second embodiment are similar to the aforementioned firstembodiment.

(Modification of Second Embodiment)

Referring to FIG. 20, in a GaN-based semiconductor laser chip 260 (260a) according to a modification of the second embodiment, two grooveportions 71 are formed on a semiconductor layer 42 to enclose both endsof a region 60, having a large number of crystal defects, of a substrate41, dissimilarly to the aforementioned second embodiment.

In a manufacturing process of the GaN-based semiconductor laser chip(device) 260 (260 a) according to the modification of the secondembodiment, two groove portions 41 b extending in a direction C are soformed on the substrate 41 as to enclose the both ends of the region 60,having a large number of crystal defects, of the substrate 41 made ofn-type GaN, as shown in FIG. 20. The groove portion 41 b is an exampleof the “third recess portion” in the present invention.

Thereafter, the layers up to a p-side contact layer (not shown) areformed on the substrate 41 similarly to the second embodiment. Thus, thetwo groove portions 71 are so formed on the semiconductor layer 42 as toenclose the both ends of the region 60, having a large number of crystaldefects, of the substrate 41, as shown in FIG. 20. In this case, the twogroove portions 71 are preferably formed so as not to protrude from endsof cleavage introduction steps 49 in a longitudinal direction (alongarrow A (along arrow B)) to the ridge portion 42 a. The groove portions71 are examples of the “first region” in the present invention. Theremaining structure and manufacturing process of the modification of thesecond embodiment are similar to those of the aforementioned secondembodiment.

Also in a structure of the modification of the second embodiment, thethickness of the semiconductor layer 42 on each of the two grooveportions 71 extending in the direction C (see FIG. 20) is smaller thanthe thickness of the semiconductor layer 42 on the region other than thegroove portions 71. Thus, tensile stress in the direction along arrow A(along arrow B) perpendicular to the direction C caused in thesemiconductor layer 42 can be relaxed by the groove portions 71, andhence microcracks can be inhibited from formation between the adjacentcleavage introduction steps 49 while locally causing steps. Thus,excellent cleavability is obtained and hence the smooth cleavage planes47 and 48 (cavity facets) can be formed. The remaining effects of themodification of the second embodiment are similar to those of theaforementioned second embodiment.

(Third Embodiment)

Referring to FIGS. 21 to 23, in a GaN-based semiconductor laser chip 300(300 a) according to a third embodiment, a selective growth stripe mask80 made of SiO₂ having an action blocking crystal growth is formed on asubstrate 41 made of n-type GaN before crystal-growing a semiconductorlayer 42, thereby forming a groove portion 81 on a semiconductor layer42, dissimilarly to the aforementioned second embodiment.

In the GaN-based semiconductor laser chip (device) 300 (300 a) accordingto the third embodiment, the semiconductor layer 42 including a ridgeportion 42 a constituting a waveguide extending in a direction C in astriped (slender) manner is formed on the substrate 41 as shown FIG. 21,dissimilarly to the aforementioned second embodiment.

According to the third embodiment, the groove portion 81 extending in adirection parallel to an extensional direction (direction C) of theridge portion 42 a is formed on the substrate 41 by side surfaces of thesemiconductor layer 42 and an upper surface of the substrate 41. Thegroove portion 81 is so formed as to have a width W0 (=about 10 μm)along arrow A from a facet of the GaN-based semiconductor laser chip 300on the side along arrow B and to have a depth D0 (=about 5 μm) from anupper surface of the GaN-based semiconductor laser chip 300 to thesubstrate 41. The groove portion 81 is an example of the “first region”in the present invention. No groove is formed on the surface of thesubstrate 41 opposed to the groove 81 dissimilarly to the secondembodiment.

According to the third embodiment, a p-side electrode 13 and a p-sidepad electrode 15 are so formed as to cover a prescribed region on anupper surface of the current blocking layer 44 made of SiO₂. Theremaining structure of the third embodiment is similar to that of theaforementioned second embodiment.

In a manufacturing process of the GaN-based semiconductor laser chip 300according to the third embodiment, the selective growth stripe mask 80made of SiO₂ having the action blocking crystal growth is formed on theflat substrate 41 in the extensional direction (direction C in FIG. 21)of the ridge portion 42 a with a prescribed thickness, as shown in FIG.22. At this time, the selective growth stripe mask 80 is so formed as tocover an upper surface of a region 60, having a large number of crystaldefects, of the substrate 41.

Thereafter the semiconductor layer 42 is formed by successively stackinga buffer layer 21 and an n-type cladding layer 22 as shown in FIG. 22.At this time, an SiO₂ mask 82 for forming a ridge portion is so formedon a prescribed region of a p-side contact layer 28 as to extend in thedirection C (see FIG. 21) after the p-side contact layer 28 is formed ona p-type cladding layer 27. Then, etching is employed for etching thep-side contact layer 28 and a prescribed region from the upper surfaceof the p-type cladding layer 27 through the SiO₂ mask 82 extending inthe direction C. Thus, the ridge portion 42 a having a width of about1.5 μm constituting the p-side contact layer 28 and a projecting portionof the p-type cladding layer 27.

As shown in FIG. 23, the selective growth stripe mask 80 and the SiO₂mask 82 are removed by wet etching with hydrofluoric acid. Thereafterthe current blocking layer 44 made of SiO₂ having a thickness of about300 nm is formed again to cover the substrate 41, from which theselective growth stripe mask 80 is removed, and the semiconductor layer42, by plasma CVD. Thus, the groove portion 81 extending in thedirection C (see FIG. 21) is formed between the adjacent semiconductorlayer 42 along arrow A (along arrow B). Then the current blocking layer44 on an upper portion of the ridge portion 42 a is removed by etching,and the p-side electrode 13 and the p-side pad electrode 15 aresuccessively formed to cover the upper portion of the ridge portion 42 aand the prescribed region of the upper surface of the current blockinglayer 44 by vacuum evaporation, as shown in FIG. 23.

Manufacturing processes of the GaN-based semiconductor laser chip 300according to the third embodiment (the remaining wafer process otherthan the wafer process described above and a separation process) issimilar to the manufacturing processes of the aforementioned secondembodiment.

In a structure of the third embodiment, the semiconductor layer 42 isnot formed on the groove portion 81 extending in the direction C (seeFIG. 21) and the thickness of the semiconductor layer 42 on this grooveportion 81 can be zero. Thus, the semiconductor layer 42 is completelydivided in the direction (along arrow A (along arrow B)) orthogonal tothe extensional direction (direction C) of the groove portion 81 withrespect to the groove portion 81 employed as the center. Consequently,tensile stress in the direction along arrow A (along arrow B)perpendicular to the direction C caused in the semiconductor layer 42can be further relaxed, and hence microcracks can be further inhibitedfrom formation between the adjacent cleavage introduction steps 49 whilelocally causing steps. Thus, excellent cleavability is obtained andhence the smooth cleavage planes 47 and 48 (cavity facets) can beformed. The remaining effects of the third embodiment are similar tothose of the aforementioned second embodiment.

(Fourth Embodiment)

Referring to FIGS. 24 to 26, a case of forming cleavage introductionrecess portions 99 (cleavage introduction steps 99 a and 99 b) havingtrapezoidal sectional shapes as viewed from cleavage plane 17 (18) in amanufacturing process (separation process) subsequent to a wafer processfor a GaN-based semiconductor laser chip (device) 400 (400 a)dissimilarly to the aforementioned first embodiment will be described ina fourth embodiment.

According to the fourth embodiment, the cleavage introduction steps 99 aand 99 b (cleavage introduction recess portions 99) having depths D4(=about 50 μm) and having trapezoidal sectional shapes as viewed fromthe cleavage plane 17 (18) are formed on the upper surface of theGaN-based semiconductor laser chip 400, as shown in FIG. 24. In otherwords, the cleavage introduction steps 99 a and 99 b are so formed thatinner side surfaces are directed toward an obliquely downward directionfrom the side of the semiconductor layer 12, and so formed as to haveplanar bottom portions on positions (depth) reaching a substrate 91 madeof n-type GaN, as shown in FIG. 24. The cleavage introduction recessportions 99 and the cleavage introduction steps 99 a and 99 b areexamples of the “first recess portion” in the present invention.

As shown in FIG. 25, steps 17 a and 18 a are formed on partial regionsof the cleavage planes 17 and 18 including the cleavage introductionsteps 99 a and 99 b in the extensional direction (direction C) of theridge portion 12 a. In other words, the cleavage introduction steps 99 aand 99 b may be formed also in an extensional direction (direction C) ofthe ridge portion 12 a in plan view (as viewed from the side of theupper surface of the GaN-based semiconductor laser chip 400), in shapeshaving steps 17 a and 18 a on parts of the cleavage planes 17 and 18.

The remaining structure of the fourth embodiment is similar to theaforementioned first embodiment. Manufacturing processes (a waferprocess and a separation process) for the GaN-based semiconductor laserchip 400 according to the fourth embodiment are similar to themanufacturing processes of the aforementioned first embodiment.

According to the fourth embodiment, as hereinabove described, thecleavage introduction recess portion 99 (see FIG. 26) having atrapezoidal shape is so formed that energy for forming an end of thecleavage introduction recess portion 99 is smaller than energy forforming the bottom portion of the cleavage introduction recess portion99, whereby a bad influence on the ridge portion 12 a (see FIG. 24)close to the end of the cleavage introduction recess portion 99 issuppressed, and deterioration of the ridge portion 12 a can besuppressed. Consequently, a length L0 (see FIG. 26) of the cleavageintroduction recess portion 99 in a longitudinal direction can be formedlonger. The cleavage introduction recess portion 99 (see FIG. 26) isappropriately so formed that an angle θ of left and right inclinedsurfaces (inner side surfaces) is in the range of about 30° to about60°, and it was possible to obtain a device having excellent lasercharacteristics in a case where the cleavage introduction recess portion99 was formed with a depth D (see FIG. 26) in the range of about 20 μmto about 60 μm when the thickness of the semiconductor laser chip was inthe range of about 100 μm to about 150 μm.

As shown in FIG. 25, the steps 17 a and 18 a are formed on parts of thecleavage planes 17 and 18, whereby separation of facet coating films canbe suppressed when the facet coating films (insulating films consistingof single-layer films or multilayer films) (shown by broken lines inFIG. 25) are formed on a light emitting facet and a reflecting facet ofthe semiconductor laser chip in the cleaved bar-shaped device, forexample. In other words, separation caused on a partial region spreadsin a wide range when a thin film is formed on the light emitting facet(reflecting facet) consisting of a completely planar surface, while thethin films strongly adhere also to the steps 17 a and 18 a when thesteps 17 a and 18 a are formed on parts of the cleavage planes 17 and 18as described above, whereby separation of the facet coating films can beinhibited from propagating to adjacent semiconductor laser chips.

Further, such steps 17 a and 18 a are so formed that the facet coatingfilms (shown by broken lines) can be inhibited from separation resultingfrom mechanical stress in bar-shaped cleavage or thermal stress in acase of operating as the semiconductor laser chip.

As to the irregularities of such steps 17 a and 18 a (depths of thesteps in a direction C in FIG. 25), at least thicknesses substantiallyidentical to the minimum values (about 50 nm, for example) of thethicknesses of the facet coating films are preferable in considerationof adherence to the facet coating films. On the other hand, cavitylength deviation may result if the irregularities of the steps 17 a and18 a are excessively large, whereby the irregularities are preferablyset to not more than about 5 nm from tolerance for dispersion of thecavity length, in consideration of a case of mounting the semiconductorlaser chip on an optical pickup, for example. The remaining effects ofthe fourth embodiment are similar to those of the aforementioned firstembodiment.

(Fifth Embodiment)

Referring to FIGS. 27 and 28, in a GaN-based semiconductor laser chip500 according to a fifth embodiment, a groove portion 530 having a depthnot reaching a substrate 511 made of n-type GaN is formed on thesemiconductor layer 12 and no groove portion is formed on a surface ofthe substrate 511 corresponding to the groove portion 530 dissimilarlyto the aforementioned first embodiment. The groove portion 530 is anexample of the “first region” in the present invention.

In the GaN-based semiconductor laser chip (device) 500 according to thefifth embodiment, the groove portion 530 extending in a directionparallel to an extensional direction (direction C) of a ridge portion 12a is formed on the semiconductor layer 12 as shown in FIG. 27. Thegroove portion 530 is so formed as to have a width W0 (=about 10 μm)along arrow A from an end of the GaN-based semiconductor laser chip 500(semiconductor layer 12) on a side along arrow B and to have a depth D5(=about 3 μm) from an upper surface of the GaN-based semiconductor laserchip 500 to the semiconductor layer 12.

In other words, in a manufacturing process of the fifth embodiment, thesemiconductor layer 12 is first crystal-grown on a main surface of theplanar substrate 511 in a wafer process, and layers from a p-sidecontact layer 28 to a part of an n-type cladding layer 22 are thereafteretched by dry etching for forming the groove portions 530, as shown inFIG. 28. Then a current blocking layer 14 (see FIG. 27) is formed tocover bottom surfaces and side surfaces of the groove portions 530.

The cleavage introduction steps 519 a and 519 b having lengths of about60 μm along arrow A (along arrow B) are formed on the substrate 511, thesemiconductor layer 12 and current blocking layer 14 to extend up to theend of the GaN-based semiconductor laser chip 500 on the side alongarrow B similarly to the aforementioned first embodiment (see FIG. 27).The cleavage introduction steps 519 a and 519 b are examples of the“first recess portion” in the present invention.

The remaining structure and manufacturing process of the GaN-basedsemiconductor laser chip 500 according to the fifth embodiment aresimilar to those of the aforementioned first embodiment. The effects ofthe fifth embodiment are similar to those of the aforementioned firstembodiment.

The embodiments and the modifications thereof disclosed this time are tobe considered as illustrative in all points and not restrictive. Therange of the present invention is shown not by the above description ofthe embodiments and the modifications thereof but by the scope of claimfor patent, and all modifications within the meaning and rangeequivalent to the scope of claim for patent are included.

For example, while each of the aforementioned first to fifth embodimentsof the present invention is applied to the GaN-based semiconductor laserchip, the present invention is not restricted to this but is alsoapplicable to a semiconductor laser device other than a GaN-based one.

While the ridge portion (waveguide) is formed on the region approachingthe first side by the distance W1 (=about 30 μm) from the center of theGaN-based semiconductor laser chip (n-type GaN substrate) in each of thefirst to fifth aforementioned embodiments, the present invention is notrestricted to this but the ridge portion may alternatively be formed ona region approaching the first side by a length other than about 30 μmfrom the center of the GaN-based semiconductor laser chip. In this case,the ridge portion is preferably formed on a region approaching the firstside by at least about 20 μm from the center of the GaN-basedsemiconductor laser chip. According to this structure, bonding of ametal wire onto the ridge portion can be suppressed also when agenerally employed metal wire having a diameter of about 30 μm is bondedto the center of the GaN-based semiconductor laser chip, whereby damageof the ridge portion (waveguide) can be suppressed in bonding.

While the cleavage introduction steps are formed on the substrate, thesemiconductor layer and the current blocking layer in each of theaforementioned first to fifth embodiment, the present invention is notrestricted to this but the cleavage introduction steps may be formed noton the substrate but only on the semiconductor layer and the currentblocking layer.

While the cleavage introduction recess portions are so formed that thecenters of the cleavage introduction recess portions are arranged on theintermediate positions between the adjacent ridge portions (waveguides)in the manufacturing process (separation process) subsequent to thewafer process for the GaN-based semiconductor laser chip in each of theaforementioned first to fifth embodiment embodiments, the presentinvention is not restricted to this but the cleavage introduction recessportions may alternatively be so formed that the centers of the cleavageintroduction recess portions are on positions other than theintermediate positions between the adjacent ridge portions (waveguides).In this case, the cleavage introduction recess portions may be formed ata prescribed interval from the ridge portions (waveguides).

While the substrate 41 made of n-type GaN linearly provided with theregion 60 having a large number of crystal defects is employed in theaforementioned second embodiment, the present invention is notrestricted to this but a substrate made of n-type GaN provided with aregion having a large number of crystal defects in a shape, such as anetwork shape, for example, other than the linear shape.

While the grooves 11 a (41 a) are previously formed on the substrate 11(41) before crystal growth of the semiconductor layer 12 to form thegroove portions 30 (70) on the crystal grown semiconductor layer 12 (42)in the manufacturing process of each of the aforementioned first andsecond embodiments, the present invention is not restricted to this butgroove portions (first regions) may be formed from the side of thesemiconductor layer 12 after the semiconductor layer 12 is grown on theplaner substrate. Also in this manufacturing process, the grooveportions formed after crystal growth are preferably formed so as not toprotrude from ends of the cleavage introduction recess portions in alongitudinal direction (first recess portions) to the ridge portions 12a (42 a). Also in the structure of this modification, tensile stress inthe direction perpendicular to the groove portion (first region) appliedto the semiconductor layer 12 can be relaxed, and hence microcracks canbe inhibited from formation between the adjacent cleavage introductionsteps (first recess portions) while causing local steps. Thus, excellentcleavability is obtained and hence the smooth cleavage planes (cavityfacets) can be formed.

While a plurality of the GaN-based semiconductor laser chips are formedto have different widths (W21, W22, W23) of the respective laser devicesalong arrow A (along arrow B) in the aforementioned second and thirdmodifications of the first embodiment, the present invention is notrestricted to this but a plurality of the GaN-based semiconductor laserchips may be formed so that widths of the respective laser devices alongarrow A (along arrow B) are equal to each other.

While the steps 17 a and 18 a are formed on parts of the cleavage planes17 and 18 in the aforementioned fourth embodiment, the present inventionis not restricted to this but the aforementioned steps formed on partsof the cleavage planes may be formed on the cleavage planes of theGaN-based semiconductor laser chip according to each of theaforementioned first to third embodiments other than the aforementionedfourth embodiment.

While the three or four GaN-based semiconductor laser chips are obtainedbetween the respective groove portions in each of the aforementionedsecond and third modifications of the aforementioned first embodiment,the present invention is not restricted to this but separation may beperformed to obtain at least five GaN-based semiconductor laser chips.

1. A method of manufacturing a semiconductor laser device, comprising steps of: forming a semiconductor layer on a surface of a substrate; forming a plurality of first recess portions; performing cleavage along said plurality of first recess portions; and forming chips by separating said semiconductor layer along a first direction parallel to said surface, wherein said semiconductor layer includes a plurality of waveguides and first regions, said plurality of waveguides are extending in said first direction, said first regions are separated from said waveguides and extend in said first direction, each of second regions are provided between each of said waveguides and each of said first regions, said plurality of first recess portions are provided in an upper surface of said semiconductor layer and extend in a second direction from said first regions to said second regions, said second direction is parallel to said surface and intersects with said first direction, a thickness of said semiconductor layer on said first region is smaller than a thickness of said semiconductor layer on said second region, and each of said chips has said waveguide on a region approaching a first side from a center of said chip in said second direction.
 2. The method of manufacturing a semiconductor laser device according to claim 1, wherein said thickness of said semiconductor layer on said first region is substantially zero.
 3. The method of manufacturing a semiconductor laser device according to claim 1, wherein said step of forming said semiconductor layer includes a step of forming said plurality of waveguides having different plural intervals and said first regions located between adjacent said waveguides having the largest interval in said different plural intervals.
 4. The method of manufacturing a semiconductor laser device according to claim 3, wherein said step of forming said semiconductor layer includes a step of forming said semiconductor layer so that third regions, having large numbers of crystal defects, of at least either said substrate or said semiconductor layer are located between adjacent said waveguides having the largest interval in said plural different intervals.
 5. The method of manufacturing a semiconductor laser device according to claim 1, wherein said step of forming said chips is performed by separating said semiconductor layer in said first regions.
 6. The method of manufacturing a semiconductor laser device according to claim 1, further comprising a step of forming second recess portions extending parallel to said first direction on a back surface of said substrate opposite to said surface of said substrate in advance of said step of forming said chips.
 7. The method of manufacturing a semiconductor laser device according to claim 6, wherein said second recess portions are formed on fourth regions opposed to said first regions, and said step of forming said chips is performed by separating said semiconductor layer in said first regions and said second recess portions.
 8. The method of manufacturing a semiconductor laser device according to claim 1, wherein said step of forming said chips includes a step of performing separation so that said surface of said substrate has said first recess portions on regions of sides opposite to said first sides of said waveguides.
 9. The method of manufacturing a semiconductor laser device according to claim 1, wherein said step of forming said first regions includes a step of forming third recess portions extending parallel to said first direction on said surface of said substrate and a step of crystal-growing said semiconductor layer on said surface of said substrate on which said third recess portions are formed.
 10. The method of manufacturing a semiconductor laser device according to claim 9, wherein said step of crystal-growing said semiconductor layer includes a step of crystal-growing said semiconductor layer to have a thickness smaller than depths of said third recess portions.
 11. The method of manufacturing a semiconductor laser device according to claim 1, further comprising step of: forming a first electrode layer formed on said surface, wherein said first electrode layer is formed at a distance from said first recess portion.
 12. The method of manufacturing a semiconductor laser device according to claim 1, further comprising step of: forming a second electrode layer formed on a back surface of said substrate opposite to said surface of said substrate.
 13. The method of manufacturing a semiconductor laser device according to claim 1, wherein said substrate and said semiconductor layer are made of nitride-based semiconductors. 